Computer



Patented Mar. 20, 1951 PATENT IC 2,545,655 GQMPUTER Irving W. Doyle, Massapequa, and Henry Erwin "gale, Freeport, -N. Y., assignors to Fairchild Gainera and- Instrument Corporation, Jamaica, Ni Y.', a corporation of Delaware Original application March 11, 1941, Seriai No. 1523,47 1, now, Patent No. 2,399,726, dateiTMay 7, 15146, Divided in! this application April 10,

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This invention relates to a method of and apparatus for computing, illustratively, for computing the lead of a machine gun or cannon as n the air s ream q i fe f n' i arrangements of parts and in the several steps and relation and order of each of the same to one or more o f the others, all as will be illustratively described herein, and the scope of the application of will be indicated in the following claims. application is a division of the copending application of Irving W l Doyle and Henry Erwin Hale, Serial No. 323,474, filed March 11, 1941 entitled Method of and'Apparatus for-Aiming a Gun, which issued on May 7, 1946, as PatentNo. 2,399,726.

In the drawing, wherein there are shown sev- .eral embodiments of our invention,

Figure l is a schematic view of a portion of our a paratu to ther t a control 6 ml tber i re;

Figure 2 is a view similar to Figure 1, but s in m sfifieo com-r0 c c tf Simil r re e en e c a cte s re er PP S m lar parts throughout the various views of the drawmg To facilitate an vwmie ta ei Q r a emruter an t ex edite t de i i t vention wil h sons sie d he ea t r a applied t ma in guns ada t d 9 be m i a un d 0. a r a t .suqhas b9m s s dirigibli i ing unde stood how v r th t the n en i i applicable to various uses wherein a number of variable conditions are encountered.

The e ar a numb r o ariable fa r in aerial gunnery which cause horizontal and vertical components of deviation between the line of fireand-the-linepf sight of the gun, and which must b com en at d for in n mgthe g n to fiec v n ide 9s Q bu let an fiar i- These factors will hereinafter he referred to asi '1- Lea r r lat yemotiq i e n of fi mus be a an an e t th i .o S ei the e i rel t ve .m q between h se? an tars sp tha the rnlea slit target? 2. Trajectory, or superelevation, i. e. the superelevation, excluding air stream eifects, of the gun nepe a rit t e ns all? Qi s o effect c incidence of bulletandtafg t Bulleflr jmp l-- a a u l mer r m the gun barrel, the rifling the'reinimparts spin t t e. bullet the b 1 if s' s i actiqn hich irb 11 5 team i eb let, causes it to precess in'a al ri 'normal'to v pp e cept when the gun is firing straight into or with m an 6am n 7 d e iet e qrieln a d fle on of t e b l et irom t ipel ne of fl h w en the.

un s mqv n at a sub an elq ily ll the air st eam rushin pas? P 1? 1. 1 mu 1 e the gun s fi in in a direct on e s i On axial with its path of movement.

The values of -.t.h s e f ctors of re atire motion, trajectory, bullet jump and w ndase a e det mined by the factors of A 1. Range (instantaneous distance between gun .aggtafg zm c J a 2. Zenith position (angle between zenith and i 7. 5: Armin ei iqn fi l c w s a l b tween lin Q si ht nne rfira 4. Inch ated air speed (hereafter referred to as a A titud e en i These latter five factors are efiective singly or in combination in determining'the values of horizon tal and vertical compor'ients of relative motion, trajectory, bullet jump and windage, as follows: A. Vertical component -1. Lead (relative motion) a. Range b. Altitude 2. Trajectory a. Range 17'. Zenith position :3 Zgiullet jump' b. Aiimuth position (zero effect when fii-mgroreana aft) c. Altitude" N b. Kliimuth position (zero effect when lfiri iig dead aldeam c. Zenith p'osi on (zero effect when d. s g h e. Altitude B. Horizontal component 1. Lead (relative motion) a. Range b. Zenith position 0. Altitude 2. Bullet jump a. IAS

17. Azimuth position (zero effect when By way of illustration, let us assume that the gun plane is flying due south at an altitude of 2,000 feet and the target plane is also flying due south on a parallel course at an altitude of 2,500 feet, that the two courses of the planes are displaced laterally 1,500 feet, and that firing commences when the planes are 1,000 feet apart horizontally. This set of conditions brings into effect both the vertical and horizontal components of relative motion, trajectory (there is no horizontal component of deviation in compensating the line of fire for trajectory), bullet jump and windage. Under these conditions, at the instant of fire, when properly aimed, the gun points upwardly, forwardly and abeam of the gun plane. Hence the line of fire must be corrected with respect to the line of sight of the gun 1. to lead the target (allow for the relative motion of the two planes),

2. to compensate for the vertical component of trajectory occasioned by the superelevation of the gun and range of the target,

3. To compensate forthe vertical and horizontal components of bullet jump occasioned by IAS, the deviation of the line of fire from both the vertical and horizontal, and,

4. To compensate for the vertical and horizontal components of windage occasioned by IAS, the deviation of the line of fire from both the vertical and horizontal, range and altitude. The corrected line of fire is accordingly the resultant of the several vertical and horizontal components modified by the range of the target and the altitude of combat. It is this complex resultant which is beyond human ability to attain with such a degree of accuracy as to effect eflicient gunnery, particularly under stress of is secured to the gun and related to the gun turret in such a manner that its horizontal and vertical components of movement are identical to those of the gun, i. e. the gun and sight move as a unit. At a focal plane within the range finder is a reticle composed of vertical and horizontal cross hairs, respectively attached to galvancmeter needles so as to move therewith. Accord ingly at the point where the hairs cross, a reference mark capable of universal planar movement is established which with the target comprises the line of sight of the gun, which can deviate relative to the line of fire thereof, as will be de scribed. As the lines of sight and fire do deviate, and as their deviation varies under certain circumstances, it will appear from the above that the deviation is proportional to the factors of lead, trajectory, bullet jump and Windage. The field of view of the range finder sight being substantially larger in area than the target plane, accordingly affords a sighting area about which the cross hairs of the reticle can be moved by the gunner, as will be described below, until the cross hairs are on the target, at which time the gun is accurately aimed.

Movement of the reticle is effected by current input to the galvancmeters, current for the galvanometer controlling the vertical cross hair, which determines horizontal deflection, being supplied from a generator geared to the turret for operation thereby. Current for the galvanometer controlling the horizontal cross hair, which determines vertical deflection, is supplied by another generator, geared to the gun or range finder in such a manner that vertical movement thereof operates its generator. Hence two control circuits are involved, one hereafter referred to as the horizontal deflection circuit, which is energized by rotation of the turret, and the other the vertical deflection circuit, which is energized by vertical pivotal movement of the gun.

From the above, it may be seen that the generator outputs are respectively proportional to the horizontal and vertical components of angular velocity of the line of sight relative to fixed axes in space as the gunner keeps his sight trained on a moving target. If, of course, the gun and target were stationary and the trajectory Of the bullet Were flat, there would be no necessity to move either the line of sight or the line of fire, and the two would coincide. Where, however, there is relative motion between gun and target, as where one airplane is firing at another, a continued deviation of the line of sight is necessary to keep it on the target. As pointed out above, this movement of the line of sight is utilized to generate electrical energy.

Also as noted above, the generator outputs are used to move the horizontal and vertical cross hairs which form the reticle. These voltages being proportional to the vertical and horizontal components of the angular velocity of the line of sight only, are not compensated for the factors of lead, trajectory, bullet jump and Windage, and accordingly must be modified in accordance therewith if the correct deviation between the lines of sight and fire is to be attained so as to aim the gun accurately.

Accordingly we modify the voltage of the vertical deflection circuit as follows:

1. For Zead.- An attenuator is connected across the generator and mechanically connected to the adjustment on the range finder. As the range finder is adjusted the resistance of the attenuator is varied so that the generator output voltage is varied by an amount proportional to the range of the instant of gun fire. A second attenuator is connected across the generator and is adjusted in accordance with the altitude. Hence, the total generator output is an approximate function oftime of flight.

2. For trajectory.Additicnal voltage is added to the circuit as by a battery, and this added voltage is metered into the circuit by at least two attenuators, one whose resistance is adjusted by the range finder adjustment, and the other whose resistance is varied by an amount proportional to the zenith position of the line of fire. The

,added to the circuit and this added voltage is metered intothe circuit by at least three attenuators. The resistance of the first is adjusted, by hand, if desired, from a reading on a voltmeter calibrated in miles per hour so that the resistance is proportional to indicated air speed- (IAS'). The resistance of the second attenuator is adjusted by a cam or other mechanism operated by the gun, sight or turret during horizontal movement thereof so that the vertical component of bullet jump is proportional to the horizontal deviation of the line of fire from the longitudinal axis of the airplane. The resistanceof the third attenuator is adjusted in accordance with altitude. When the line of fire is fore or aft of the airplane in a horizontal plane, the vertical component of bullet jump is zero.

4. For windage.Additional voltage is added to the circuit, and this added voltage is metered into the circuit by five attenuators, so that the value of the voltage added is a product of several voltages of the several attenuators. The resistances of these attenuators are adjusted in accordance with IAS, azimuth position, zenith position, range and altitude, so that the vertical component of windage may be said to be proportional to these several factors.

The value of the vertical deflection voltage is impressed on the galvanometer which controls the horizontal cross hair so that the horizontal crosshair is moved to a position which effects devia'tion of the line of fire oi the gun from the line. of sight in such a manner that the vertical component of angular velocity of the line of fire is proportional to the vertical component of linear velocity of the target. Hence, the line of fire of the gun is caused to correctly lead the target in so far as the vertical component of lead is concerned.

The voltage of the horizontal deflection circuit isv modified as follows:

1. For lead, or relative mtion.-An attenuator, whose resistance is varied by the range finder adjustment, is connected across the generator so that the output thereof is proportional to the range. Furthermore, the horizontal com-- ponent of lead or relative motion is eiiected by the vertical position of the gun. Hence, an attenuato-r, the resistance of which is varied according to the guns zenith position is also connected across the generator further to modify its output. As altitude is a factor here, a third attenuator adjusted in accordance with altitude-isconnected across the generator.

2. For bullet y'ump.Additional. voltage is added to the circuit, and the value of? this voltage is determined by the product of. the outputs of at. least four attenuators, the resistances of which are respectively adjusted in accordance with indicated air speed, azimuth position, zenith position and altitude. Hence, the component of horizontal deflection of the line of sight to compensate for bullet jump is proportional to IAS, azimuth and zenith positions and altitude, as stated.

3. For windage.Additiona1 current is added to the circuit and the voltage of this current is a product of the voltages of at least four attenu ators whose resistances are varied respectively, according to-indicated air speed, horizontal position, range and altitude.

6; The horizontal deflection. voltage is impressed on the second galvanomet'er which controls the position of the vertical crosshair, so that when the line of sight is varied to set the vertical cross hair on the target, the correct deviation is imparted tothe line of fire so as to impartthereto the proper component of horizontal deflection, and hence to compensate the line of fire for the several factors which anect it. Hence, the horizontal component of angular velocity of the line of sight imparts to the line of fire a horizontal component of angular velocity which is in turn proportional to the horizon-talcomponent of linear velocity. of the target. The resultant of the horizontal and vertical components of angular velocity of the line of fire, as determined by the similar components of angular velocity of the line of sight, is proportional to the resultant of the horizontal and vertical components of linear velocity of the target so that the line of fire leads the target by a correct amount.

In other words, when the gunner sights his target, he moves his range finder, and accordingly his gun, until the reticle formed by the cross hairs is on the target. This movement, as described above, energizes the two circuits, causing movement of the reticle so as to cause deviation between. the line of sight and line of fire, which deviation accurately aims the line of fire so as to impart thereto a lead which is corrected for the several factors which must be compensated for if bullet and target are to meet.

It should be noted, however, thatin a system as above described, the angular velocity of the lines of fire and sight is not necessarily constant,

but might well be accelerating, in which casethe angle of'defiection between the gun and the line of sight will be increasing. Under such circumstances, the line of sight moves backward with respect to the line of fire by an amount which is proportional to the angular acceleration of the line of fire of the gun, i. e. the rate of change of angular velocity of the line of fire; Therefore; the angular velocity of the line of sight is the algebraic sum of the instantaneous angular velocity of the line of fire; plus the backward instantaneous angular velocity of the line of sight with respect to the-line of fire. The correct deflectionbetween the line of sight and the line" of fine should be proportional to the angular velocity of the line of sight; but the actual defiection is proportional to the angular velocity of the gun. Therefore, an error is introduced in this deflection which is proportional to the angular velocity of the line of sight relative to the gun, and which is also proportional to therate of change of angular velocity of the gun. To compensate or correct for this error, voltages are introduced into the horizontal and vertical deflection circuits in the opposite direction to that of the current flowing therein as a result of gun movement, and this counter E. M. F. is proportional to the rate of change of angular velocity of the gun. This counter E. M. F. may be introduced in each circuit as by a suitable self inductance, such as a choke coil, the number of effective turnsof' which are preferably varied in accordance with variations in range andaltitude, so that the counter E. M. F. is proportional to time of flight.

Referring now to Figure 1, wherein there is schematically shown a movably mounted gun, vertical and horizontal deflection control circuits which are energized inaccordance with gun movement, and a reticle, the movement of which is responsive to the control circuits energization, the gun is generally indicated at and is mounted on a suitable horizontal support 2| capable of rotation in a horizontal plane. The gun is also pivoted to a vertical support 22 extending upwardly from support 2| for movement in vertical planes. A gear sector 23 is secured to gun 20 for operation of a train of gears generally indicated at 24, connected to a generator 25. Support 2| may have teeth out therein for operation of a train of gears generally indicated at 26, connected to a generator 21. Generator 25 energizes the vertical deflection circuit, whereas generator 21 energizes the horizontal deflection circuit.

Vertical deflection circuit 1. Relative motion.--A pair of lines 28 and 29 are connected to the opposite sides of generator 25, and lead to opposite sides of an attenuator 30, being connected to terminals 3| and 32 of the attenuator resistance 33. Attenuator includes a slider arm 34 adapted to slide along resistance 33 to vary the generator output, and as arm 34 is connected to the range finder adjustment referred to hereinabove and described below, the value of resistance 33 is proportional to the range.

A line 2|8 connects .slider 34 with resistance 2|| of another attenuator generally indicated at 2|2, resistance 33 of attenuator 30 being connected by a line 2 I3 to the other side of resistance 2|| of attenuator 2|2.

Attenuator 2|2 includes a slider 2|4 adapted to slide along resistance 2H, and this slider is manually adjustable in accordance with a reading taken from the airplanes altimeter. A line 35 is connected to slider 2|4, while a line 36 is connected to resistance 2| of attenuator 2 I 2, and as will now appear, the voltage across lines 35 and 36 is the generator output modified in accordance with the range and altitude, and hence is proportional to the lead necessary to correct for relative motion between gun and target. Line 35 is connected to a self inductance or the like, such as a choke coil 31, this coil being connected by a line 38 to one side of a galvanometer generally indicated at 39. The armature of the galvanometer has mounted thereon a post 40 from which extend arms 4| and 42, to the free ends of which is connected a horizontal cross hair 43. Upon energization of the galvanometer, cross hair 43 moves in a vertical plane to indicate vertical deflection in proportion to the voltage of the vertical deflection circuit.

2. Traject0ry.-Line 36 is connected to a line 44, in turn connected to the slider 45 of an attenuator generally indicated at 46. Attenuator 46 has a resistance over which slider 45 is positionable in accordance with variations in the zenith position of gun 2D, movement of which causes movement of slider 45, as will be more particularly described hereinbelow. Terminal 48 of resistance 41 is connected by a line 49 to a slider 50 of an attenuator generally indicated at 5|, and having a resistance 52. This attenuator is similar to attenuator 30, and its slider arm 50 is connected to slider arm 34 of attenuator 30, so that manual adjustment of the range finder is reflected in movement of arm 50 along resistance 52.

Attenuators 5i and 46 aresupplied with cur-- rent by a battery 53. Hence, it will appear that the output of attenuator 5| is connected to at tenuator 46, and the product of the outputs ofboth is added to the voltage across lines 35 and 36. The total voltage thus flows through a line 54 connected to attenuators 46 and 5| and bat-* tery 53, and hence the added voltage across lines 44 and 54 is proportional to the range and to the drop of the bullet from its projected line of 1 fire, excluding windage eilects.

3. Bullet jump.-Line 54 is connected to a line 55, in turn connected to a slider 2|5 adapted to ride over the resistance 2|6 of an attenuator generally indicated at 2|1. Slider 2 l5 is adjustable in accordance with a reading from the airplanes altimeter, and is preferably mechanically linked, as indicated by the dotted line |35, to altitude attenuator 2|2. Resistance 2|6 of attenuator 2 H is connected by a line 2 I8 to the slider 56 of an attenuator generally indicated at 51.

Attenuator 51 includes a circular resistance 58 having a terminal 59 connected by a line 60 to a slider 6| adapted to slidably engage a resistance 62 of an attenuator generally indicated at 63. One side of resistance 62 is connected by a line 64 to one side of battery 53, the other side of the battery being connected to a line 65 connected to the side of resistance 62, and also to a terminal 56 on resistance of attenuator 51.. A voltmeter is connected to lines 6!] and 65 across battery 53, and is calibrated in miles per hour, so that slider iii of attenautor 63 may be accurately adjusted to render the output of attenuator 63 proportional to indicated air speed. Slider 56 of attenuator 5'! is mechanically or otherwise connected, as will be described in detail below, to gun 28, or it is mounted in such a fashion that horizontal movement of the gun effects movement of slider 56, so that the resistance 58 of attenuator 51 is modified in accordance with the component of horizontal gun deflection. As the gun is usually positioned to fire from either the port or starboard beam of the airplane, attenuator 51 is of a character as to reverse the current flow therefrom in accordance with the direction of fire of the gun. Thus, attenuator slider 56 is also connected to a line 2|9, in turn connected to the other side of resistance 2|6 of attenuator 2|1. This latter side of resistance 2H5 is connected to a line 68, so that the additional voltage across lines 55 and 68 is proportional to the vertical component of bullet jump, the value of which is determined by indicated air speed, azimuth position of the gun, and altitude. In this connection it should be noted that when the gun is firing directly lore or aft in a horizontal plane, there is no vertical component of bullet jump or, for that matter, any horizontal component. Hence, when the gun is firing fore or aft, attenuator slider 56 would be horizontal, as viewed in Figure 1, so that the product oi the outputs of attenuators 51 and 63 is zero.

4. Windage.-I iine 68 is connected to a line 69, in turn connected to a slider 10 of an attenuator generally indicated at 1|, having a resistance 12 connected by a line 13, in turn connected to a slider 14 of another attenuator generally indicated at 15. Resistance 16 of attenuator 15 is connected by a line 11 to a slider 18 adapted to slide about a resistance 19 of an attenuator generally indicated at 89. Resistance 19 and the last-referred to attenuator is connected by a line 8| to the slider 62 of another attenuator generally indicated at 63, and having a resistance 84. Resistance 84 of attenuator 33 is connected by a line 85 to a slider. 86 of an attenuator 81, whose resistance 88 is connected by a line 89 to one side of battery 53. The other side of battery 53 is connected by a line 90 to the other side of resistance 8B, and also to resistance 84 of attenuator 83. A line 9i connected to slider .82 of .attenuator 83 is also connected to resistance IQ of attenuator 8G, and the slider I8 of this latter resistance is connected by a line 92 to resistances 75 and 12 of attenuators I and 'II, respectively. The resistance of attenuator "Ii is manually adjustable in accordance with a reading from the altimeter [not shown] on the airplane, and hence its resistance is proportional to altitude. The resistance of attenuator "i5 is adjusted upon adjusting the range finder, and hence its resistance is proportional to range. Attenuator is mechanically connected to attenuators 30 and M, the three attenuators operating together as indicated by the dotted line 93.

Attenuator 85 is connected mechanically or otherwise to gun so that its resistance is varied as the zenith position of the gun is varied. Attenuator 83 is, as noted above with respect to attenuator 57, adjusted upon horizontal movement of the gun, while attenuator :8! is set in accordance with indicated air speed as read from voltmeter 6'? connected across battery 53. Hence it will appear that the added Voltage across lines 69 and 62 is modified in accordance with indicated air speed, azimuth position, zen th position, range and a-ltituda'all of which determine the value of the factor or windage.

Line 92 is connected to the other side of galvanometer 39, and it accordingly will appear that the voltage across lines 38 and 92 is proportional to the vertical components of relative motion, trajectory, bui-let jump and windage.

Before going into the description of the horizontal deflection circuit, it should be noted in connection with attenuators 8B and 83 that the output of attenuatorBll is reversed as the .gun swings past the horizontal, whereas the output of the attenuator '83 is reversed as the gun swings fore and aft of its dead abeam position. 'It should further be noted that the output of attenuator 89 is zero when the gun is firing in a horizontal plane, as there is no component of vertical deflection in so far :as'windageis concerned, when the gun .is laid horizontally. Also, when the gun is firing dead abeam on either side of the airplane, the output of attenuator 83 is zero as there is no component of vertical deflection when the gun is firing dead abearn. Preferably, the vertical deflection circuit provided with a manually operable switch 9:3 which can be opened by the gunner when the .gun is not in use, to preserve battery 53.

Preferably We provide another manually operated switch, such as switch 95 in line 92, which may be opened when desired to deenergize the entire vertical deflection circuit so that the gun may be aimed and fired without reference to the automatic gun sight.

Horizontal deflection circuit 1. Relative motion.--Generator 27, which generates current upon horizontal movement of gun 20, is connected by lines 95 and 91 to the ends of a resistance 98 of an attenuator generally indicated at 99. This attenuator includes a slider I'BO which, through the mechanical linkage indicated by dotted line 53, is adjustable along resistance 9.8 in accordance with adjustment of the range finder, so that the output of attenuator 99 is proportional to range. Slider 32B is connected by a line 'lfil to "the resi tance 122 of another attenuator generally indicated at $03, re-

sistance I02 also being connected to line 9], At-

. 10 tenuator I03 includes a slider I04 which, through the mechanical linkage indicated .by dotted line 105, is connected to the sliders of attenuators 46 and 80. Accordingly, the resistance of attenuator I03 is varied in accordance with movement of.

gun 20 in vertical planes. Attenuator slider 1.04 is connected to a line 220, in turn connected to a resistance 22:I .of an attenuator generally indicated .at 222, theslider 223 of which is connected to a line I06. The other side of resistance 22I of this attenuator is connected by a line .224 to line .91, line 224 also being connected to a line 225. and hence the voltage across lines 225 and I06 is the output of generator 2'! as modified in accordance with range, zenith position and altitude. which together determine the value of the horizontal component of lead due to relative motion.

2. Bullet jump-To compensate for the horizontal component of bullet jump, current is added to the horizontal deflection circuit from battery 53 by way of lines 191 and H18, the former being connected to line 4-06. Battery 53 is connected by .lines I09 and I II) to the resistance III of an attenuator generally indicated at II2, havingan adjustable slider I l.3 adapted to be hand set in accordance with indicated air .speed, as described above in connection with attenuator 63. Slider H3 is connected by a line :H 4 to one terminal of a resistance H5 of an attenuator generally indicated at I16, resistance 1 I5 also being connected to line IN]. Resistance 1 I5 is varied by a slider I H which is linked mechanically orotherwise to the sliders of attenuators 5! and 83, so that the resistance of attenuator H6 is determined by the azimuth position of the gun.

Slider I? of attenuator H6 is con-nected by lines H 8 and H9 to the resistance I20 of an attenuator generally indicated at I.2I, which has a slider I22 mechanically linked to the sliders of attenuators 46, and $9.03, as indicated by dotted line H35, so that the resistance of attenuator I2I is determined by the zenith position of the gun. Slider I22 of attenuator I.2I is connected by a line 226 to the resistance 22? of an attenuator generally indicated at 228, the slider also being connected to the other side of this resistance by a line 229. Attenuator -228 includes a slider 230 which is preferably mechanically linked, as indicated by line I35, to the other altitude attenuators, so that adjustment thereof as heretofore described adjusts altitude attentuator 228. Resistance 22-1 of the latter attenuator is also connected to line IB'I. The added voltage across lines In! and I 08 is accordingl modified in accordance with indicated air speed, azimuth position, .zenith position and altitude, which together determine the value of the horizontal component .of bullet ump.

It should be noted, in connection with this portion of the circuit, that .the output of attenuator H6 is zero when the gun is firing dead abeam, as in this position there is no horizontal component of deflection in so .far as bullet Jump is concerned. Also, the output of attenuator l2I is zero when the gun is firing in a horizontal plane, regardless of direction, as again there can be no horizontal component of deflection in connection with bullet jump. .It should further be noted that the outputs of attenuators Hi5 and I2I are reversed respectively as the gun swings past the dead abeam position, or passes from above .to below the longitudinal axis of the plane, or vice versa.

3. Windage.'1he horizontal deflection circuit Voltage is further modified by the addition there- 11 to of current from battery 53 connected to the circuit bylines I23 and I24, the former being connected to line I08. This additional current is controlled as to value by attenuators whose resistances are adjusted in accordance with indicated air speed, azimuth position, range and altitude, these attenuators being indicated generally at I25, I26, I21 and I28, respectively. Their respective sliders are connected with the sliders of the attenuators of similar type, as described above. Thus, slider I28 of the IAS attenuator I is connected as by mechanical linkage, indicated by dotted line I29, to attenuators 53, 81 and H2, all of these attenuators accordingly being manually adjusted until the voltmeter 67 connected thereacross gives a reading equal to the indicated air speed of the airplane. Slider I30 of attenuator I26 is connected to the sliders of attenuators 57, 83 and IIS as by mechanical linkage indicated by the dotted line I3I, all of these attenuators being adjustable upon movement of the gun horizontally. Slider I32 of attenuator I2? is connected to the other attenuators, adjusted upon adjustment of the range finder through the mechanical linkage indicated by dotted line 93. Similarly, slider I34 of attenuator !28 is connected by mechanical linkage indicated by the dotted line I35 to slider I0 of attenuator II, so that all of the altitude attenuators are adjusted simultaneously from a reading taken from the airplanes altimeter. Hence it follows that the modification of the voltage added to the horizontal deflection circuit across lines I23 and I24 is in accordance with indicated air speed, azimuth position of the gun, range and altitude, which determine the horizontal component of windage.

In connection with attenuator I25, it should be noted that the output thereof is zero when the gun is firing directly fore or aft, as under such circumstances there is no horizontal deflection in so far as windage is concerned. Furthermore, the output of this attenuator reverses as the gun is swung from port to starboard, or vice versa. The horizontal deflection circuit, furthermore, can be completely deenergized through manual operation of a switch I36, which may be connected to line I24.

Line 225 is connected to a choke coil I3'I, in turn connected by a line I38 to one side of a galvanometer generally indicated at I39. Line I24 is connected to the other side of galvanometer I39. The galvanometer armature is connected to a post I40, from which extend arms MI and I42, to the free ends of which is connected a cross hair I43, which extends vertically and indicates horizontal deflection as the galvanometer energization varies.

It will now appear that cross hairs 43 and M3, the positions of which are controlled respectively by galvanometers 39 and I 35, comprise the reticle hereinbefore referred to, which is visible in a focal plane of the range finder, all as will be described in detail hereinbelow.

From the above description of the vertical and horizontal deflection circuits, it may be seen that as the gunner trains his sight on the target, he must move both his range finder and gun, as the target moves, in order to keep the line of sight on the target. This movement, of course, operates generators 25 and 21, resulting in the energization of the two circuits which, of course, causes movement of the reticle formed by cross hairs 43 and I43. As pointed out above, the line of sight deviates from the line of fire, and this results because of the modifications to the deflection circuits which are made to compensate for the factors of relative motion, trajectory, bullet jump and windage. Hence, when the gunner has his line of sight on his target, his line of fire deviates therefrom by an amount suflici nt to properly lead the target so that bullet and target meet.

It will also appear that as the sight and gun are moved, angular velocities are imparted to the line of sight and line of fire, which are constant so long as the angular velocity of the gun remains constant. When, however, the guns angular velocity accelerates, the value of the voltages in the deflection circuits is increased, and this increase would cause the line of sight and line of fire to deviate, in effect causing the line of sight to move relative to the line of fire in a direction reverse to that of the line of fire. If this condition were not corrected, it would not be possible for the gunner to get his line of sight on his target. To counteract this action of the line of sight, a counter E. M. F. is introduced in each of the circuits, and this counter E. M. F. is proportional to the rate of change of angular velocity of the gun. Choke coils 31 and I31, in Figure 1, being of proper characteristics, introduce in each of the circuits the proper counter E. M. F. to counteract the relative backward movement of the line of sight from the line of fire, upon an acceleration in the angular velocity of the line of fire.

While the horizontal and vertical deflection circuits shown in Figure 1 are series circuits, the various groups of compensating attenuators may be connected in parallel. Furthermore, where there are in one circuit a substantial number of attenuators having variable resistances, it is pref erable that each attenuator be of the so-called T-pad type, as will be described below, by the use of which the desired results are attained without varying the total circuit resistance. To this end, we have provided the vertical and horizontal deflection circuits shown in Figure 2, Wherein the same number and grouping of attenuators are used as in Figure 1, but the groups are connected in parallel, and the individual attenuators are of the T-pad type.

Vertical deflection circuit With reference to Figure 2, generator 25 (the vertical deflection generator) is connected by wires I44 and I45 to the input terminals I46 and I4! of an attenuator of the T-pad type, generally indicated at I48. Attenuator I48 includes a vari able resistance I49, connected across generator 25, and a pair of fixed series resistances I50 and I5I, and a variable resistance I52, shunting fixed resistances I50 and I5I. Attenuator or T-pad I48 may include one or more fixed balancing resistances, such as resistance I53. Variable resistances I49 and I52 are provided with contact sliders I54 and I55, so associated with their respective resistances that the output of attenuator I 48 across its output terminals I56 and I5! may be varied without varying the total resistance of the circuit.

Attenuator output terminals I56 and I51 are respectively connected to lines 239 and 23I, in turn connected to the input side of an attenuator generally indicated at 232. This attenuator is also of the T-pad type, and accordingly is capable of a variable output without causing a change in the total circuit resistance. Attenuator 232 is manually adjusted in accordance with a reading from the airplane altimeter, and its output side is connected to lines I58 and I59.

Line I58 is connected to one terminal I60 of a self inductance generally indicated at I 6|, the other terminal I62 of which is connected by a line I63 to one side of galvanometer 39. Inductance I6I is provided for the same purpose as choke coil 31 (Figure 1), i. e. to introduce into the circuit a counter E. M. F. which is proportional to the rate of change or the acceleration of the angular velocity of the line of sight as hereinbefore described. Inductance I6I preferably includes a balancing fixed resistance I64, connected to a variable resistance I65, in turn connected to a coil I66, the coilbeing connected to inductance terminal I62. Also connected to inductance terminal I62 by a line I61 is a contact arm I68 adapted to selectively engage one of several coil taps I69. Re- 'sistance I65 is provided with a slider I16 which varies the resistance of resistance I65 with respect to that of coil I66, as contactor I68 engages one or another of coil taps I 69, so as to maintain the total resistance of inductance I6I constant. Slider I10' and contactor I68 are mechanically linked so as to be capable of the stated operation. Also, slider I16 is mechanically linked as indicated by the dotted line IN to sliders I53 and I54 of attenuator I48. Linkage I1I is connected with the manual adjustment on the range finder, as described below, so that when the gunner adjusts his range finder he automatically adjusts attenuator I48 so that the output thereof as across lines I58 and I59 is proportional to lead due to relative motion, the value of which is determined by range and altitude. Thus the line of fire is corrected for the factor of relative motion.

The vertical deflection circuit output is further modified by the addition thereto of current, which additional current is in turn modified in accordance with the factors of, trajectory, bullet jump and windage, in much the same manner as that described above in connection with Figure 1. Thus, to provide vertical deflection to compensate for trajectory, we provide a pair of attenuators generally indicated at I12 and I13, the product of the outputs of which is carried by lines I'M and I15 to lines I16 and I 11. The output of these attenuators is supplied from a battery 233 across which the attenuators are connected. These latter two lines connect respectively with lines I53 and I59, and accordingly feed into galvanometer 39. Attenuator I 12 is connected by the mechanical linkage I'II with attenuator I48, and accordingly is operated therewith upon the gunners manipulation of his range finder. Attenuator I13 is mechanically linked to gun 25, for example, as by mechanical linkage indicated by the dotted line I19, so that movement of the gun in vertical planes varies the resistance of attenuator I13.

To compensate for bullet jump, additional current is fed into lines I56 and $59 from a battery 235 through lines I19 and I86, which are respectively connected to lines I16 and I11. The value of the current across lines I i9 and I86 is modified in accordance with indicated air speed, azimuth position and altitude, respectively by attenuator generally indicated at IEI, I82 and 235. Attenuator I52 is connected to attenuator 235, in turn connected to lines, I19 and I89, preferably by a reversing switch I83, so that the output of the attenuator may be automatically reversed in direction when the gun swings from port to starboard, or vice versa. The output from attenuator I82, being related to the azimuth position of the gun is, of course, zero when the gun is firing fore 14 and aft, as in that position there is no vertical component of bullet Jump.

Still further current is fed into lines I58 and I 59 from battery 236 by Way of a pair of lines I84 and I 85 connected respectively to lines I16 and I11. The value of the current across lines I84 and I is a function of indicated air speed, azimuth position, zenith position, range and altitude, the compensations necessary for these factors being determined by the attenuators generally indicated at I66, I81, E88, E89 and I96. Attenuator I86 is similar to attenuator I'8I, being connected thereto as by a mechanical linkage indicated by the dotted line I9I, this mechanical linkage being manually operable by the gunner in accordance with the indicated air speed or the airplane. The azimuth position attenuator I81 is mechanically connected to attenuator I82 as by a mechanical linkage indicated by the dotted line I 92, so that the two attenuators are adjusted together upon horizontal movement of the gun.

The output of attenuator I81 is shifted in direction when the gun swings past dead abeam position, by a reversing switch I83 which connects the azimuth position attenuator I81 to the zenith position attenuator I88. The latter attenuator is similar to attenuator I13, and is mechanically linked thereto by linkage I16 so as to be adjusted therewith upon vertical movement of gun 26. As gun 25 is capable of shooting both above and below the horizontal axis of the airplane, the output of zenith position attenuator I88 must be reversed when the gun swings from above the axis a .to a point below it, and to this end a reversing switch I94 is provided.

Reversing switch 564 connects attenuator I88 with attenuator E89, the resistance of which latter attenuator is adjusted with that of attenuator I48 upon manual adjusment of the range finder. These two attenuators are mechanically linked by linkage I'II. The resistance of the altitude attenuator I98 is varied manually by the gunner in accordance with a reading taken from the airplane altimeter, the adjustment being efiected by suitable mechanical linkage, as indicated by the dotted line I65.

From the above, it will appear that the various compensations for the vertical components of deflection of the factors of relative motion, trajectory, bullet jump and windage, are introduced fied by the action of inductance I6I as described,

the current impressed on galvanometer 39 results in a deflection of cross hair 43, which causes a -vertical deflection of the line of fire suflicient to impart the necessary vertical component of lead to the gun with respect to the target.

Horizontal deflection circuit As noted above with respect to the description of the horizontal deflection circuit of Figure 1, there are horizontal components of deflection in connection with the factors of relative motion between gun and target, bullet jump and windage,

which must be imparted to the line of fire if it is to lead the target correctly, or, stated another way, the horizontal components of relative motion, bullet jump and windag must be allowed for, if the gun is to be correctly aimed. To this end, we have provided the horizontal deflection circuit shown in Figure 2, wherein the vertical cross hair I43, controlled by galvanometer I39, is deflected by an amount proportional to the horizontal component of angular velocity of the un, modified by the horizontal components of relative motion, bullet jump and windage. As these modifications are efiected in the circuit of Figure 2 in substantially the same manner as described above in connection with the horizontal deflection circuit in Figure 1, it will suffice to say that the relative motion compensation results from the adjustment of range, zenith position and altitude attenuators I96, I91 and 231; bullet jump compensation is effected through the adjustment of indicated air speed, azimuth position, zenith position and altitude attenuators I98, I99, 260 and 238, respectively, windage compensation being effected by indicated air speed, azimuth position, range and altitude attenuators MI, 202, 203 and 204, respectively. The group of relative motion attenuators I96, I91 and 231 modify the output of generator 21, the group of bullet jump attenuators I98, I99, 200 and 23B modify the additional current from battery 239, while the windage attenuators 2UI264 modify a furtheraddition of current from battery 240. All of these attenuators are, of course, preferably of the T-pad type, such as hereinbefore described, and accordingly the variation in their resistances have no effect on the total circuit resistance, which remains constant. The horizontal deflection circuit also includes an inductance 205, similar to inductance I6I to correct for rate of change of the horizontal component of angular velocity of the line of fire. It will now appear that the vertical and horizontal deflection circuits of Figure 2 react in substantially the same manner as those in Figure l, to correctly deviate the line of fire from the line of sight so that the gun leads the target by a correct amount.

As pointed out hereinabove, inductances I6I and 205 are provided to vary the outputs of their respective circuits so that the deviation of the horizontal and vertical cross hairs will be corrected for the error introduced by the rate of change of the angular velocity of the line of fire. It should be noted in this connection, however, that in the place of these inductances (not shown) suitable transformers may be used to attain th desired end. Such a transformer would include a primary coil connected in the particular circuit involved, and a secondary coil (not shown) connected to a coil provided in the galvanometer which would when energized introduce a torque counter to that resulting from energization of the main circuit. Where such a transformer is used, it is desirable to connect into the circuit connecting the secondary coil with th counter torque galvanometer coil, a suitable attenuator similar to the T-pads shown in the circuits of Figure 2, so that the output of the transformer secondary could be modified in accordance with tim of bullet flight as determined by range and altitude.

It will be noted that in the description of the circuits shown in Figure 2, we have assumed that the voltages of the several batteries would be fixed and constant in value. If the actual voltage varies, however, from the desired value, suitable voltage controls must be introduced into the circuits to vary the voltages as desired. A voltmeter or other suitable indicating device may be provided to indicate that these controls are set at the proper value.

We claim:

1. In apparatus for automatically computing a desired value bearing a predetermined complex relationship to a plurality of variable conditions, in combination, means to create an electric quantity whos value is a function of the instantaneous value of one of said conditions, means to modify the value of said electrical quantity in accordance with variations in one or more of said conditions, means to create a second electrical quantity whose value is independent of said conditions, means to modify said second electrical quantity in accordance with variations in one or more of said conditions, means to combine said modified electrical quantities to produce a third electrical quantity, and means to modify said third quantity by an amount proportional to the rate of change of value of said third electrical quantity thereby to produce an ultimate value bearing the desired complex relationship to Said conditions.

2. In apparatus for automatically computing a desired value having a predetermined complex relationship to a plurality of independently variable conditions, in combination, means to produce an electrical ,potential which is a function of the instantaneous value of one of said conditions, means to attenuate said potential in accordance with variations in one or more of said conditions to produce a first product voltage, means to create a second electrical potential, means to attenuate said second electrical potential in accordance with the instantaneous value of one or more of said conditions to produce a second product voltage, means to combine said first and second product voltages to produce a third potential, circuit means to derive an electrical current from said third potential, and means to produce an electromotive force opposing chang of value of said current and proportional to the rate of change thereof.

3. Apparatus according to claim 1 wherein said means to attenuate comprises one or more resistance networks each variable in accordance with the value of a particular one of said conditions.

4. Apparatus according to claim 1 wherein said means to attenuate comprises one or more T-pad resistance networks each variable in accordance with the value of a particular one of said conditions.

5. In apparatus for computing a desired value having a predetermined relationship to the values or to the rates of change of values of a plurality of variable conditions, in combination, means to produce a first electrical potential the value of which is a function of the rate of change of one of said conditions, means to attenuate said first electrical potential in accordance with variations in the values of one or more of said conditions, means to produce a second electrical potential, means to attenuate said second electrical potential in accordance with changes of the values of one or more of said conditions, one or more of which are the same as said first mentioned conditions, means to combine said attenuated electrical potentials to produce a third electrical potential, circuit means to produce an electrical current from said third electrical potential, and means to modify said electrical current by an amount proportional to the rate of change of said current to produce a modified electric current the value of which bears the desired rela tionship to said conditions.

6. In apparatus for determining a desired instantaneous value which is a function of the voltage having a predetermined relationship to the particular conditions controlling said first and second attenuators; generating means to provide a secondary primary potential; a third attenuator connected to said second primary potential and adapted to be controlled in accordance with the instantaneous value of one of said conditions to produce a second reference potential which is a function of the condition controlling said third attenuator; means for combining said first and second reference potentials; circuit means coupled to said combined voltage for deriving a current therefrom; and means for introducing in said circuit means an electromotive force of said polarity as to oppose any change in value of said current and having a magnitude proportional to the rate of change of said current, whereby said resulting current is proportional to said desired value.

7. In apparatus for determinin a desired instantaneous value which is a function of the combined values of two or more variable potentials the values of which are in turn functions of the values of a plurality of variable primary conditions, in combination, generating means to provide a fixed value primary potential; a first constant current, voltage attenuator coupled to said primary potential and adapted to be controlled in accordance with the instantaneous value of one of said conditions; a second constant current, voltage attenuator coupled to the output of said first attenuator and adapted to be controlled in accordance with the instantaneous value of one of said conditions to produce a first reference voltage having a predetermined relationship to the particular conditions controlling said first and second attenuators; generating means to provide a second primary potential; a third constant current, voltage attenuator connected to said second primary potential and adapted to be controlled in accordance with the instantaneous value of one of said conditions to produce a second reference potential which is a function of the condition controlling said third attenuator; means for combining said first and second reference potentials; circuit means coupled to said combined voltage for deriving a current therefrom; and means for introducing in said circuit means an electromotive force of such polarity as to oppose any change in value of said current and having a magnitude proportional to the rate of change of said current, whereby said resulting current is proportional to said desired value.

8. An electrical control circuit for producing an electrical current the value of which bears a predetermined relationship to the magnitudes of two or more conditions, comprising a first and a second generating circuit for producing a first and a second primary control potential; each of said generating circuits comprising a source of electrical potential and a plurality of condition responsive circuits each adjusted in accordance with the instantaneous value of one of said conditions and coupled in series relation to said electrical potential and adapted to divide said potential successively in accordance with the instantaneous values of the respective associated conditions to produce said first and second primary control potentials; means for combining said control potentials to produce a secondary control potential; means for deriving a current from said secondary control potential; and means for producing an electromotive force opposing change in said current, said electromotive force being proportional in magnitude to the rate of change of said current.

9. An electrical control circuit for producing 0nd primary control potentials, each of said generating circuits comprising a source of electrical potential and a plurality of condition responsive circuits each adjusted in accordance with the instantaneous value of one of said conditions and each coupled in parallel relation to its associated electrical potential and adapted to produce an electrical current in accordance with the instantaneous values of the respective associated conditions, means to combine the currents from each of the condition responsive circuits which comprise each generating circuit to produce first and second control currents, means to combine said currents to produce a final control current, and means for producing electromotive forces opposing any changes in said final control current, said electromotive forces being proportional in magnitude to the rate of change of said current.

IRVING W. DOYLE. HENRY ERWIN HALE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,584,182 Methlin May 11, 1926 1,893,009 Ward Jan. 3, 1933 2,070,178 Pottenger Feb. 9, 1937 2,208,609 Stover July 23, 1940 2,217,639 Blackburn Oct. 8, 1940 2,251,973 Beale Aug. 12, 1941 2,317,419 Taylor Apr. 27, 1943 2,363,588 Enns July 6, 1943 FOREIGN PATENTS Number Country Date 164,765 Great Britain June 23, 1921 218,548 Great Britain July 10, 1924 237,217 Great Britain Nov. 26, 1925 476,831 Great Britain Dec. 16, 1937 598,068 France Sept. 16, 1925 248,330 France July 24, 1939 

